1. Technical Field
The present invention pertains to surgical scalpels and, more particularly, to a surgical scalpel having a movable protective shield.
2. Discussion of the Prior Art
Surgical scalpels are sometimes provided with a blade shield or guard to protect against accidental cutting of operating room personnel during handling of the scalpel. Such protection has become critically important in recent years in view of the epidemic nature of the AIDS virus being spread by intermixing very small amounts of blood. It is important, however, that the blade guard or shield be selectively movable by the surgeon to expose the blade for cutting without causing unnecessary or uncomfortable hand movement by the surgeon, and without unduly complicating or enlarging the scalpel structure. In this regard, a surgeon typically holds a scalpel between the thumb and the facing side of the middle finger with the forefinger disposed along the top surface of the scalpel. Since the forefinger is typically the most precisely controlled finger on one's hand, it is desirable to provide a blade shield that can be moved into and out of extended position by a simple movement of the surgeon's forefinger without requiring movement of the thumb or middle finger, and without requiring repositioning of the unit in the surgeon's hand. It is also desirable that the scalpel be capable of being manufactured at sufficiently low cost to be disposable after a single use, thereby eliminating the need to sterilize the scalpel after each surgical procedure.
The prior art discloses a variety of surgical scalpel structures that reflect attempts to address the above-described considerations. For example, U.S. Pat. No. 2,735,176 (Costin) discloses a surgical knife having a hollow handle serving as a sheath for a blade disposed for slidable extension and retraction between cutting and shielded positions. Movement of the blade requires the surgeon to at least rearrange the handle in his/her hand and, in most cases, requires two-handed actuation. Further, sheath-type scalpels generally require complex locking and retraction mechanisms, resulting in a cost that is significantly higher than is practical for disposability. The scalpels disclosed in U.S. Pat. Nos. 3,905,101 (Shepard) and 3,906,626 (Riuli) have sheaths in which a handle carrying the blade is slidable between protective and cutting positions, but require two hands to effect the sliding motion.
The scalpel disclosed in U.S. Pat. No. 5,071,426 (Dolgin et al) includes a blade guard having an actuating mechanism that is automatically contacted by the surgeon's thumb and forefinger when these fingers are placed along opposite sides of the scalpel handle. This finger position is described in the Dolgin et al patent as being the normal position in use of the scalpel, even though many surgeons generally prefer the position described above wherein the thumb and the facing side of the middle finger are disposed on opposite sides of the handle, and the forefinger is disposed along the top edge of the handle. Nevertheless, the Dolgin et al guard actuation mechanism is a somewhat complex structure comprising an actuating arm extending at an acute angle from the rear end of the handle and terminating in a linkage assembly extending entirely across the handle to project transversely from the opposite side of the unit. In one embodiment the linkage includes a first rack movable transversely when the actuator is squeezed in order to rotate a first pinion mounted inside the handle on a common axle with a second pinion. The second pinion drives a second rack disposed on the blade guard to move the blade guard longitudinally in response to transverse actuator movement. The ratio of teeth on the respective pinions provides a mechanical advantage permitting the second rack to move a greater distance than the actuator rack. The transverse projecting actuator and linkages make the unit somewhat cumbersome and unwieldy as well as difficult to store efficiently. Moreover, the transversely projecting linkage is subject to being misaligned during storage or mishandling, resulting in the failure of the actuating mechanism. Further, the complexity of the overall actuating mechanism itself renders the mechanism susceptible to failure.
The surgical scalpel of the present invention obviates the above-described problems of the prior art by providing a disposable scalpel having a blade shield capable of selective extension and retraction without movement of the surgeon's hand from the preferred cutting position and without requiring a complex and inconvenient structure.